Proton-exchange membrane fuel cells are well known. In a PEM fuel cell, hydrogen atoms are ionized in an anode, migrate through a specialized membrane as hydrogen cations (protons), and combine with oxygen anions at a cathode to form water. Electrons from the hydrogen flow from the anode through an external circuit to the cathode, performing work in between. The membrane, typically with a catalyst coating sandwiched between layers of gas diffusion media (GDL), is know in the art as a membrane electrode assembly (MEA). A bipolar plate assembly is constructed by joining an individual anode and cathode plate.
Fuel cell assemblies comprise a plurality of individual bipolar plate assemblies stacked together and connected in electrical series. When the MEA is captured between the anode and cathode they form an individual cell whereby the electrochemical reaction can take place. Such bipolar plates, when stacked together with the MEAs in between, form a fuel cell assembly. Openings through the bipolar plates near the edges form headers for inlet and exhaust of fuel and combustion gases as well as coolant. Other openings may be provided for alignment during assembly or for other specialized purposes.
Bipolar plates typically are formed of a metals (such as titanium or stainless steel) or composites (such as a thermoset graphite-loaded vinyl ester polymer) and are easily damaged by twisting or other application of uneven stresses. The plates require a non-conductive seal or gasket along all outer edges and around all openings to prevent leaking of reactant gases and coolant and to electrically insulate the bipolar plates from each other. It is known to use separate die-cut or molded elastomeric gaskets, installed between the plates during assembly of a fuel cell stack.
A problem exists in locating the gaskets properly with respect to the openings to be sealed. Further, individual gaskets are thin, very pliable, and thus are easily twisted and deformed. A misaligned or twisted gasket can cause leaks, broken bipolar plates, and stack failure.
What is needed is a reliable method of forming and installing resilient gaskets in assembly of a fuel cell stack.
It is a principal object of the present invention to improve the reliability of assembly of a fuel cell stack.
It is a further object of the invention to reduce waste and cost in fuel cell manufacture.
It is a still further object of the invention to improve ease of assembly of a fuel cell stack.